>>13219195I dunno about Turtwig. He doesn't seem really useful during the campaign of the game, despite how much of a boss his final evolution is.
Infernape can basically carry the game on his own, and Empoleon's one of possibly two good water type Pokemon available in 4th gen's campaign.
Of course, my list doesn't really consider the rankings of Brokemon. Obviously all the grass starters are pretty cool, but there are often other worthy grass types to use.